Evidence for evolution: Fossils

• What should you be able to do by the end of this video?

  Discover fossils and provide evidence for evolution
• Why are fossils important in studying evolution?

  They provide evidence for evolution
• What are fossils?

  Remains of organisms from millions of years ago
• How can fossils form when parts of organisms have not decayed?

  Conditions needed for decay are absent
• What conditions can prevent decay of organisms?

  Cold temperatures, lack of oxygen, lack of water
• What happens to organisms that decay during fossil formation?

  Parts can be replaced by minerals
• What are preserved traces of organisms?

  Footprints or spaces left by roots
• Why are there very few fossils of early life-forms?

  Soft-bodied organisms rarely form fossils
• What has happened to many fossils of early life-forms?

  They have been destroyed by rock changes
• What does the lack of early life-form fossils mean for scientists?

  They cannot be certain how life began
• What does it mean for a species to be extinct?

  No remaining individuals of that species alive
• What can cause a species to become extinct?

  Catastrophic events, environmental changes, competition
• How can environmental changes lead to extinction?

  Changing weather patterns or new diseases
• How can competition lead to extinction?

  More successful species compete for resources
• What are the three ways fossils can form?

  1. Parts of organisms do not decay
  2. Organism decays but parts are replaced by minerals
  3. Preserved traces like footprints or root spaces
• What are the reasons for the scarcity of early life-form fossils?

  • Soft-bodied organisms rarely fossilize
  • Many fossils destroyed by geological changes
  • Limited conditions for fossil formation
• What are the main reasons species become extinct?

  • Catastrophic events (e.g., asteroid impact)
  • Environmental changes (e.g., new diseases)
  • Competition with more successful species